PR 39, a porcine 39-aa peptide antibiotic, was originally isolated from the upper part of the small intestine of the pig. PR 39 is compsed of 49% proline and 24% arginine, and 19 of which are proline and 10 of which are arginine. And it is a group consists of linear peptides containing a very high proportion of certain amino acids, especially proline and arginine, is one of the largest group of antibacterial peptides. PR 39 has antibacterial activity against Gram-negative bacteria and is equivalent to tetracycline. PR-39 belongs to the cathelin family of peptide antibiotics but not an inhibitor of thiol proteases, and 10 different peptide antibiotics have been found so far, including cathelin proparts in pig.
Different from the antibacterial mechanism of most other antibacterial peptides, PR39 does not kill bacteria by destroying and lysing the cell membrane of bacteria, but penetrating into the bacteria and inhibiting the synthesis of DNA and protein. In terms of antibacterial effect, because of its special antibacterial mechanism, the researchers found that the antimicrobial peptide PR39 has broad-spectrum antibacterial effects against microorganisms such as Gram-positive bacteria, Gram-negative bacteria and Mycobacterium tuberculosis. PR 39 was found to be a growth factor in wound healing and an inhibitor of reactive oxygen species production via steric inhibition of the NADPH oxidase complex. Moreover, PR 39 was also found to be involved in the ubiquitin-proteasome pathway by blocking the degradation of IκBα without affecting overall proteasome activity.
PR39 is secreted in a preproprotein form that contains a leader sequence and its -NH2 terminal portion is rapidly cleaved into a mature active form that is involved in wound healing and protection against myocardial ischemia. In addition, PR 39 has many additional functions such as neutralizing endotoxin, anti-inflammatory effection, immune induction, tissue repairing and apoptosis inhibition, excepting its broad-spectrum and efficient antibacterial activity to bacteria including Salmonella Typhi and Mycobecterium Tuberculosis. Compared with traditional antibiotics, PR39 has multi-aspect advantages for the therapy of bacterial infection, and it is expected to be a new antibiotic against intracellular bacterial infection.
1. Gudmundsson, G. H., Magnusson, K. P., Chowdhary, B. P., Johansson, M., Andersson, L., & Boman, H. G. (1995). Structure of the gene for porcine peptide antibiotic PR-39, a cathelin gene family member: comparative mapping of the locus for the human peptide antibiotic FALL-39. Proceedings of the National Academy of Sciences, 92 (15), 7085-7089.
2. Ramanathan, B., Wu, H., Ross, C. R., & Blecha, F. (2004). PR-39, a porcine antimicrobial peptide, inhibits apoptosis: involvement of caspase-3. Developmental & Comparative Immunology, 28 (2), 163-169.